The word “printer” as used herein encompasses any apparatus, such as a digital copier, book marking machine, facsimile machine, multi-function machine, etc., that produces an image with a colorant on recording media for any purpose. Printers that form an image on a surface of an image receiving member and then transfer the image to recording media are referenced in this document as indirect printers. Indirect printers typically use intermediate transfer, transfix, or transfuse members to facilitate the transfer and fusing of the image from the image receiving member to the recording media. In general, such printing systems typically include a colorant applicator, such as a printhead, that forms an image with colorant on the image receiving member. Recording medium is fed into a nip formed between the surface of the image receiving member and a transfix roller to enable the image to be transferred and fixed to the print medium so the image receiving member can be used for formation of another image.
In solid ink imaging systems having intermediate image receiving members, ink is loaded into the system in a solid form, either as pellets or as ink sticks, and transported through a feed chute by a feed mechanism for delivery to a heater assembly. A heater plate in the heater assembly melts the solid ink impinging on the plate into liquid ink that is delivered to a printhead for jetting onto a surface of an image receiving member. In the printhead, the liquid ink is typically maintained at a temperature that enables the ink to be ejected by the inkjet ejectors in the printhead, while preserving sufficient tackiness for the ink to adhere to the surface of the image receiving member. In some cases, however, the tackiness of the liquid ink can cause a portion of the ink to remain on the surface of the image receiving member after the image is transferred onto the media sheet. This remnant of the jetted image can later degrade other images formed on the surface of the image receiving member.
Solid inkjet imaging systems generally use electronic image data to generate firing signals for the ejection of melted ink to produce the ink image. In indirect solid inkjet imaging systems, like printer 300 shown in FIG. 5, the electronic image data are used to eject ink onto the surface of an intermediate image receiving member 304. A media sheet 308 is then brought into contact with the image receiving member 304 in a nip 312 formed between the image receiving member 304 and a transfer roller 316. The heat and pressure in the nip 312 helps transfer the ink image from the image receiving member 304 to the media sheet 308.
One issue arising from the transfer of an ink image from an image receiving member 304 to a media sheet 308 is the build-up of ink on the image receiving member 304. Build-up of ink on the image receiving member 304 can cause various image defects because ink that remains on the image receiving member 304 from a previous print can be unintentionally transferred to the media sheet 308 in a subsequent print. Accordingly, reducing the build-up of ink on the image receiving member 304 improves the efficacy of the printer and the quality of the prints.
To address the build-up for ink on the image receiving member 304, release agent is applied to the image receiving member 304 in a thin layer prior to the application of ink to the image receiving member 304. The release agent is a substance which prevents the ink from adhering directly to the image receiving member 304, facilitating the proper transfer of the ink from the image receiving member 304 to the media sheet 308 when the media sheet 308 passes through the nip 312. Release agent is typically applied to an image receiving member 304 at levels greater than 10 mg/sheet, and various release agent applicators 320 have been designed to properly apply the correct amount of release agent to the image receiving member 304.
One way that release agent is applied to an image receiving member in the amounts noted above is with a release agent roller as shown in FIG. 6. In this embodiment, the printer 2 includes a pivot shaft 4 permanently mounted within the printer 2 and a pivot arm 8 permanently mounted to the pivot shaft 4. The pivot arm 8 rotates about the pivot shaft 4. In this embodiment, the release agent roller 12 is a foam roller formed from an absorbent material that is saturated with release agent. The release agent roller 12 is saturated with a supply of release agent to be used for the life of the release agent roller 12. The release agent roller 12 is provided within a tray 20. The tray 20 is coupled to the pivot arm 8 and rotates around the pivot shaft 4 to move the release agent roller 12 in and out of contact with the image receiving member 28. The release agent roller 12 and the tray 20 are coupled together as a single unit. Together, the release agent roller 12 and the tray 20 are removed from the printer to be replaced by a new tray 20 having a new release agent roller 12 that is fully saturated with release agent to replenish the supply of release agent. For removal and replacement, the tray 20 is configured to slide into and out of connection with the pivot arm 8 in a direction aligned with the pivot shaft 4, but does not slide along the pivot shaft 4.
A wiping blade 32 is also mounted to the pivot shaft 4 to rotate around the pivot shaft 4. In this embodiment, the wiping blade 32 is permanently mounted within the printer 2 and is positioned within the tray 20. The wiping blade 32 is not replaced with the tray 20 and the release agent roller 12. The wiping blade 32 rotates into and out of contact with the image receiving member 28 to wipe excess release agent from a surface 36 of the image receiving member 28. Excess release agent is collected in the bottom of the tray 20 to be absorbed by a thin foam pad 16. The foam pad 16 presses against the release agent roller 12 with enough pressure to return excess release agent to the release agent roller 12, but not with enough pressure to prevent the release agent roller 12 from rolling in contact with the image receiving member. A filter 40 is located between the foam pad 16 and the release agent roller 12 and removes particulates from the excess release agent before the release agent is reabsorbed by the release agent roller 12.
To apply release agent to the surface 36 of the image receiving member 28, the entire tray 20 is rotated to move the release agent roller 12 toward the image receiving member 28 until the release agent roller 12 contacts the surface 36 of the image receiving member 28. The release agent roller 12 then applies release agent to the surface 36 of the image receiving member 28, the metering blade 32 removes excess release agent from the surface 36 of the image receiving member 28 and deposits it in the tray 20. Once the release agent has been applied to the surface 36 of the image receiving member 28, the tray 20 moves away from the image receiving member 28 to move the release agent roller 12 out of contact with the image receiving member surface 36 to prevent interference with the imaging process and disturbance of the image that is laid down over the layer of release agent on the image receiving member 28.
While this release agent roller system provides release agent to the image receiving member 28 in an effective amount, it also suffers from some limitations. One limitation arises from the supply of release agent being contained within the system. Once the supply of release agent is exhausted, the printer needs to be serviced and either the release agent roller 12 or the entire tray 20 removed and replaced. Additionally, because all of the release agent used in the release agent roller system is contained within the tray 20 or the release agent roller 12, which is also provided within the tray 20, the tray 20 is heavy. Thus, moving the tray 20, including the release agent roller 12 toward and away from the image receiving member 28 also involves moving a large, and heavy, supply of release agent requiring a more powerful actuator and more energy.
As described above, applying release agent to the surface of an image receiving member with a release agent applicator is effective at preventing the presence of unwanted ink on the image receiving member. Additionally, using release agent reduces the need for maintenance. Also, supplying the release agent to the image receiving member in an efficient manner reduces the energy needs of the printer. Accordingly, providing a release agent application system which enables efficient use of release agent and enables proper application of release agent on the image receiving member while requiring little energy to apply the release agent to the image receiving member is a desirable goal. Reducing the amount of energy required to apply release agent to the image receiving member, in turn, enables reduction in size, cost, and noise associated with the application of release agent. Reducing the amount of waste generated over the lifetime of a printer that uses a release agent application is also desirable.